The present invention relates to a sealing apparatus and, more particularly, to a sealing apparatus for component parts of a vehicle, particularly, for component parts of a tractor or the like which are rotatable in either of two directions.
Known sealing apparatuses of this type include a sealing apparatus as shown in FIG. 5A. The sealing apparatus 100 has the following construction. A rotary shaft 101 is rotatable in the direction of arrow, i.e. in the counter-clockwise direction, as viewed on the left side of the figure. A slinger 102 is fitted around the rotary shaft 101 and has a side surface 103 extending in the radial direction. The sealing apparatus 100 has a housing 104 on which a sealing apparatus main body 105 is mounted. A sealing lip 106 extends from the sealing apparatus main body 105 and is in sliding contact with a portion of the side surface 103 of the slinger 102, so as to seal oil which serves as a sealed fluid and which is on the B (right) side of the apparatus, as viewed in FIG. 5A. It is known in general that a sealing apparatus, such as the apparatus 100, in other words an end seal, does not possess the so-called pumping action, i.e., the action of sucking in air on the A (left) side of the apparatus, as viewed in FIG. 5A, to the sealed fluid (oil) side, to thereby prevent the oil from leaking. Therefore, it is general to provide a thread 107 on a portion of the side surface 103 of the slinger 102 so that air on the side A is forcibly sucked in by the apparatus (see FIG. 5B).
Japanese Utility Model Publication No. 55580/1982 discloses another conventional sealing apparatus, as shown in FIG. 6, in which a thread is also provided on a side surface of a slinger. According to this disclosure, a rotary shaft 111 is partitioned by a partitioning member 112 into the oil side B (the right side as viewed in FIG. 6) and the atmospheric air side A (the left side as viewed in the figure). A rotary member 115 is secured to the rotary shaft 111. A seal ring 116 is secured to the partitioning member 112 by means of a fixing member 117, and the tip 161 of the seal ring 116 is in contact with a side surface 151 which is at the tip of the rotary member 115 and is closer to the partitioning member 112. The fixing member 117 opposes a hook-shaped portion 152 of the rotary member 115 with a small gap 171 between, and it is provided with a groove 172 which is adjacent to the seal ring 116 and is recessed radially inward of the tip 161.
With the conventional sealing apparatus having the above-described construction, oil in the oil side B is sealed from the atmospheric air side A by virtue of the annular contact between the tip 161 of the seal ring 116 and the side surface 151 of the rotary member 115, the side surface being closer to the partitioning member 112.
The above-described prior art, however, encounters the following disadvantages. With the conventional sealing apparatus shown in FIGS. 5A and 5B, since the thread 107 is directed in such a manner as to allow air to be sucked in to the oil side when the rotary shaft 101 rotates in the above-mentioned counterclockwise direction, oil on the side B is sucked out when the rotary shaft 101 rotates in the opposite direction. Therefore, this sealing apparatus can be used only at locations where the direction of rotation is constant, for instance, at a location in an engine.
With the conventional sealing apparatus shown in FIG. 6, when the rotary shaft 111 remains stationary, oil may leak through the thread provided on the side surface of the slinger. In order to prevent this problem, an oil trap, such as the groove 172, has to be formed, thus causing an increase in the number of processes required for manufacturing the apparatus and an increase in production costs.